Fig. 5. Burrow nesting is correlated to behavioral sensitivity to DMS. (A) Southern giant petrel (Macronectes giganteus) brooding a chick on a surface nest. Photograph courtesy of R. Van Buskirk. (B) White-chinned petrel (Procellaria aequinoctialis) incubating an egg in its dark, underground burrow. Photograph provided by G.A.N. (C) Marginal probability reconstructions of ancestral states for nesting habit and DMS responsiveness using the topography of Nunn and Stanley (Nunn and Stanley, 1998). Each tree uses a global analysis and a Markov k-state one-parameter model (Pagel, 1999). Areas of pie charts indicate relative support for each ancestral state. Positive DMS attraction indicates those species that showed a statistically significant behavioral response to DMS in experimental trials. Log likelihood scores for the trees are –6.869894700 for nesting habit and 7.607159452 for DMS behavioral sensitivity. All reconstructions are significant for the ancestral state occupying the majority of each node, except for two nodes labeled as not significant (NS) [reproduced with permission from Van Buskirk and Nevitt (Van Buskirk and Nevitt, 2008)].